1. Field
This patent specification relates to an electrophotographic image forming apparatus in general and, in particular, to such apparatus incorporating a contact and detachment mechanism for facilitating maintenance and parts exchange workability in addition to the improvement in image qualities.
2. Discussion of the Background
The electrophotographic image forming process is well known. In image forming apparatuses such as a copying machine, printer and facsimile apparatus, the formation of the images is generally carried out through the electrophotographic process steps of forming electrostatic latent images on an image bearing member or photoreceptor, which is provided with several image forming process members such as a charging unit, developing unit and so on in the circumference of the photoreceptor.
In the charging unit, a charging roller is included more often recently which is formed to be brought into contact with the photoreceptor in a similar manner to a developing roller in the developing unit.
In case of a color image forming apparatus, the tandem-type structure is often adopted among several methods for implementing color image forming process steps, in which a photoreceptor and image forming process members associated thereto is provided for each of the color components, Y (yellow), M(magenta), C(cyan) and Bk(black).
The steps of latent image formation, development and image transfer are carried out for respective color components so as to be in proper timing with the revolution of the respective photoreceptors. As a result, a full color image can be formed in a manner of proper registration, on a transfer member (second image bearing member) utilized in common to these colors.
The thus formed full color image on the transfer member is subsequently transferred onto a recording member such as, for example, a sheet of copy paper.
In such image forming apparatus, several disadvantages are encountered such as for example, the appearance of contact residual images which is caused in formed images as the remainder of continual contact between the photoreceptor and the image forming process members such as transfer belt, charging unit and developing unit, and which is likely to degrade image quality.
In another example, when image formation on a large number of sheets of paper is carried out continuously, the temperature increases in the vicinity of image forming unit and this increase may reach such a level that causes a thermal expansion in the sheet member, thereby resulting in change in resultant images (for example, undue image expansion and/or image slippage).
This change may become evident in cold district, in particular, where is subjected to severe decrease during night hours and increase in succeeding morning hours, thereby making it hard for the units in the apparatus to properly follow the temperature, and also causing dew condensation with relative ease. As a result, the quality of resultant images may again be degraded.
In order to obviate such difficulties, several improvements can be made such as, for example, respective photoreceptors are provided detachably with respect to, and then removed arbitrary from, the transfer belt.
However, because of further parts to be included in the detachable mechanism, for example, this measure may result in more complicated structure and costs increase. In addition, this attempt may decrease workability on the apparatus of a maintenance and/or parts exchange for a user or service personnel, whereby another difficulty may arise.
As to the image forming apparatus attributed servicing and replacement feasibility, there have been previously known are those with maintenance and parts exchange capability by a user, in which photoreceptor and developing unit are formed integrally and provided detachably from the apparatus, such as called as the process cartridge type (or process unit type), as disclosed previously in Japanese Laid-Open Patent Application No. 11-161113.
The process cartridge type offers several advantages such as, for example, the ease of maintenance and parts exchange operations on arriving at operating life because of the above noted integral construction formation. At the same time, this results a disadvantage as well, in which the cartridge has to be replaced in its entirety when any one of the constituent units arrives at its life and even when some of constituent unit are still usable, to thereby decreases recycling efficiency for respective constituents. As a result, this may result in costs increase and additional burden to the environment.
In addition, as disclosed in Japanese Laid-Open Patent Application No. 11-161113, mishandling may occur during parts exchange steps with regard to plural image forming units, in which a unit for a certain color may erroneously be replaced by that of different color. Although it is therefore desirable to provide the means for obviating such mishandling, this may cause additional increase in machine costs for the image forming apparatus.
After these feature and feasibility of the cartridge-type structure, a trend is becoming more versatile, that is, the trend to replace each of constituents up to individual operation life, called durable disassembly type, from the previous unit disposable type.
The durable disassembly type of construction, however, may encounter several difficulties such as, for example, because of an increased number of parts in the full color image forming apparatus of the tandem type, in particular, operations of maintenance and/or parts exchange become quite complicated and difficult for the user or service personnel.
It is therefore an object of the present disclosure to provide a relatively simple, less expensive contact/detach mechanism for an image forming apparatus of the tandem type construction having a plurality of image bearing members. The contact/detach mechanism is capable of obviating undue effect from continual contact such as, for example, contact residual images. The mechanism also facilitates to improve the workability on the apparatus of a maintenance and/or parts exchange for the user or service personnel by handling a plurality of units simultaneously, when necessary, to thereby reducing the frequency and/or labor hours for the handling the units.
In regard to the units feasible of being replaced by a user or service personnel, there may be cited are the aforementioned photoreceptor and the image forming process members such as developing unit, charging unit, and so on, and in combination thereof as a process unit. In addition, further units are also cited among the above units for image forming apparatus in particular such as a sheet feeding unit and fixing unit, which are suffered more often by jamming of the sheets of paper than other units.
In case when any maintenance and/or parts exchange work is needed for the units above mentioned, the apparatus is designed to designate specific unit(s) on a display device provided on operation panel of the image forming apparatus, whereby the user is urged, for example, to take necessary measures for the maintenance or parts exchange.
As to the display devices, Japanese Patent Application No. 2000-79745 discloses a device for movie displays, Japanese Laid-Open Patent Application No. 11-231729 a display device for instructing operation steps and the sequence thereof, and Japanese Patent Application No. 2000-53275 both overall and detailed images of the portion to be subjected to the operation steps.
The user can generally carry out necessary operation steps by recognizing the display contents shown and then implementing necessary maintenance and/or parts exchange operation steps according to the contents.
In the course of the operation for the maintenance and/or parts exchange, although the user may memorize once the display contents and then carry out operation steps according to own recollection, one may not be able to either find the exact location, recall the specific content, or follow the exact sequence.
In another instance, a schematic diagram displayed on the panel may not show the correlation to the actual parts in the apparatus clearly enough to implement necessary operation steps smoothly and thoroughly.
It is therefore another object of the present disclosure to provide display means for an image forming apparatus, capable of clearly displaying the location to be presently subjected to maintenance and/or parts exchange operation, and also instructing operation steps and the sequence thereof, if necessary, in a manner clearly recognized and easily correlated to the actual parts in the image forming apparatus.